Over the past few decades, cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP) and cyclic di-guanosine monophosphate (c-di-GMP) have been well studied. These signaling molecules play important biological roles in prokaryotes and their eukaryotic hosts (Gomelsky, 2011, Kalia et al., 2012). In contrast, cyclic di-adenosine monophosphate (c-di-AMP) was recognized only recently as a potential new second messenger in a structural study of DisA by Karl-Peter Hopfner's group in 2008 (Witte et al., 2008). Similar to the paradigms to the other cyclic nucleotides, synthesis, degradation, and secretion of c-di-AMP have been reported in various bacteria, which opens up a new field of research addressing the molecular basis of c-di-AMP network.
Cyclic di-adenosine monophosphate (c-di-AMP) is synthesized from ATP catalyzed by diadenylate cyclase (DAC) and cleaved to pApA or AMP by phosphodiesterase. In bacteria, c-di-AMP levels are precisely maintained; both absence and over-production of c-di-AMP have been shown to be detrimental to several bacteria. The biological roles of c-di-AMP include peptidoglycan homeostasis, resistance to antibiotics and stress conditions, repair of DNA damage and sporulation, and regulation of biofilm formation. c-di-AMP effector proteins have been identified in both prokaryotic and eukaryotic cells. Additionally, c-di-AMP secreted by bacteria induces a type I interferon response in host cells. Therefore, this molecule plays an essential role in bacterial physiology and pathogenesis.
However, the study of c-di-AMP is largely limited due to the lack of a simple but sensitive method for detection. Presently, the detection method commonly used is a liquid chromatography-mass spectrometry (LC-MS)-based analysis, which is relatively complicated.
The tremendous current interest in the biological role of c-di-AMP dictates the need for a sensitive, accurate, and readily performed procedure for estimation of its cellular levels. The methods currently available do not have the extreme sensitivity required by the low tissue levels of the compound, or else they are laborious to perform, or both.
Thus, a need exists for a fast, cost effective, reliable method for the measurement of c-di-AMP.